ASTM E1438-06
(Guide)Standard Guide for Measuring Widths of Interfaces in Sputter Depth Profiling Using SIMS
Standard Guide for Measuring Widths of Interfaces in Sputter Depth Profiling Using SIMS
SIGNIFICANCE AND USE
Although it would be desirable to measure the extent of profile distortion in any unknown sample by using a standard sample and this guide, measurements of interface width (profile distortion) can be unique to every sample composition (1, 2, 3).3 This guide, that describes a method that determines the unique width of a particular interface for the chosen set of operating conditions. It is primarily intended to provide a method for checking on proper or consistent, or both, instrument performance. Periodic analysis of the same sample followed by a measurement of the interface width, in accordance with this guide, will provide these checks.
The procedure described in this guide is adaptable to any layered sample with an interface between layers in which a nominated element is present in one layer and absent from the other. It has been shown that for SIMS in particular (4, 5) and for surface analysis in general (6, 7), only rigorous calibration methods can determine accurate interface widths. Such procedures are prohibitively time-consuming. Therefore the interface width measurement obtained using the procedure described in this guide may contain significant systematic error (8). Therefore, this measure of interface width may have no relation to similar measures made with other methods. However, this does not diminish its use as a check on proper or consistent instrument performance, or both.
SCOPE
1.1 This guide provides the SIMS analyst with a method for determining the width of interfaces from SIMS sputtering data obtained from analyses of layered specimens. This guide does not apply to data obtained from analyses of specimens with thin markers or specimens without interfaces such as ion-implanted specimens.
1.2 This guide does not describe methods for the optimization of interface width or the optimization of depth resolution.
This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.
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Designation: E1438 – 06
Standard Guide for
Measuring Widths of Interfaces in Sputter Depth Profiling
1
Using SIMS
This standard is issued under the fixed designation E1438; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope mechanical or electronic gating. The intensity of one or more
secondary ions is monitored with respect to time as sputtering
1.1 This guide provides the SIMS analyst with a method for
continues.
determining the width of interfaces from SIMS sputtering data
4.2 The interface width is then determined from the second-
obtained from analyses of layered specimens. This guide does
ary ion intensity versus time data according to an arithmetic
not apply to data obtained from analyses of specimens with
model described in the Procedure section. A measurement of
thin markers or specimens without interfaces such as ion-
the thickness of the layer overlying the interface is required.
implanted specimens.
This measurement may be performed by another analytical
1.2 This guide does not describe methods for the optimiza-
technique.
tion of interface width or the optimization of depth resolution.
1.3 This standard does not purport to address all of the
5. Significance and Use
safety concerns, if any, associated with its use. It is the
5.1 Although it would be desirable to measure the extent of
responsibility of the user of this standard to establish appro-
profile distortion in any unknown sample by using a standard
priate safety and health practices and determine the applica-
sample and this guide, measurements of interface width (pro-
bility of regulatory limitations prior to use.
file distortion) can be unique to every sample composition (1,
3
2. Referenced Documents 2, 3). This guide, that describes a method that determines the
2
unique width of a particular interface for the chosen set of
2.1 ASTM Standards:
operating conditions. It is primarily intended to provide a
E673 Terminology Relating to Surface Analysis
method for checking on proper or consistent, or both, instru-
3. Terminology
ment performance. Periodic analysis of the same sample
followed by a measurement of the interface width, in accor-
3.1 Definitions:
dance with this guide, will provide these checks.
3.1.1 SeeTerminology E673 for definitions of terms used in
5.2 The procedure described in this guide is adaptable to
SIMS.
any layered sample with an interface between layers in which
4. Summary of Guide
anominatedelementispresentinonelayerandabsentfromthe
other. It has been shown that for SIMS in particular (4, 5) and
4.1 This guide will allow interface widths to be calculated
for surface analysis in general (6, 7), only rigorous calibration
fromplotsofSIMSsecondaryionintensityversustimethatare
methods can determine accurate interface widths. Such proce-
acquired during sputtering of layered specimens. It assumes
dures are prohibitively time-consuming. Therefore the inter-
that a primary ion beam with a stable current density is being
face width measurement obtained using the procedure de-
used. Briefly, these plots are obtained in the following fashion:
scribed in this guide may contain significant systematic error
an ion beam of a particular ion species, ion energy, and angle
(8). Therefore, this measure of interface width may have no
of incidence is used to bombard a sample.The beam is rastered
relation to similar measures made with other methods. How-
or defocused so as to attempt to produce uniform current
ever, this does not diminish its use as a check on proper or
density in the analyzed area, that is defined by means of
consistent instrument performance, or both.
6. Apparatus
1
This guide is under the jurisdiction of ASTM Committee E42 on Surface
6.1 The procedure described in this guide can be used to
Analysis and is the direct responsibility of Subcommittee E42.06 on SIMS.
Current edition approved Nov. 1, 2006. Published November 2006. Originally determine an interface width from data obtained with virtually
approved in 1991. Last previous edition approved in 2001 as E1438 – 91 (2001).
any SIMS instrument.
DOI: 10.1520/E1438-06.
2
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
3
Standards volume information, refer to the standard’s Document Summary page on The boldface numbers given in parentheses refer to a list of references at the
the ASTM website. end of this guide.
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